Cold weather kills electric car range

When the weather outside is frightful (including very hot), battery car performance suffers.

The Nissan Leaf can lose 40 percent of its range on the worst day of the year. (Nissan photo)

California resident Sam Miller-Christiansen just loves his 2014 Chevy Volt, which he calls “my little Zen garden on wheels.” But he’s “always longed for better electric range” than the 38 miles his car achieves on a good day. For 2016, Chevrolet listened to the feverish testimony of Volt owners and jumped that battery mileage to 50.

Sam Miller-Christiansen has no major range issues: He lives in the best state for EVs, California, and drives a range-extended Chevy Volt. (Photo: Chevrolet)

Range is a huge issue with EV owners, and for very good reasons. The Volt has the gas engine in reserve, but 100 miles is the standard top end for battery electrics. And that’s only under optimal conditions; bad weather makes the range much worse.

A new study published in Environmental Science and Technology (EST) looks at the range-and-weather equation, and reports, based on driver testimony, that cold days (using the heater) or very hot ones (air conditioning) can reduce range up to 40 percent. Remember that gas cars generate their own electricity for accessories like that; in electrics, everything drains the battery. Also, batteries simply aren’t as efficient in extreme weather (especially if they lack pack heating and/or cooling).

And I’ve seen much the same in winter EV driving — the 100-mile car becomes the 60-mile (at best) car. A Volt I drove during a New England winter went 28 miles before switching to the gas engine, which isn’t bad — Nissan Leaf and Mitsubishi i-MiEV cars I drove did much worse under frigid conditions. One December, I got 34 miles from an i-MiEV that’s rated at 62. Mitsubishi has warned i-MiEV drivers not to use the heater because it will cut the range in half; a refreshed 2016 model may improve that dilemma.

I like heat in the winter (and air conditioning in the summer), which is one reason my results are worse than average. Patrick Wang, a San Francisco Volt owner, told me that 40-degree weather reduced his range modestly to 34 miles, and he compensates by pre-warming the car while it’s plugged in at home, then setting the heater to low.

EST’s research suggests that that in a city with a moderate climate, such as San Francisco, the median range for a Nissan Leaf battery electric is around 76 miles, and it’s above 70 miles more than 99 percent of the time. In a super-hot city like Phoenix, it can drop to 49 miles on the worst day of the year, while in super-cold Rochester, Minnesota, a 36 percent range drop was observed. Even within a big state like California, there can be energy-consumption-per-mile variations of 18 percent because of differences in weather.

Range (in all weather) is king, and that’s why the Tesla Model S’ 265 miles is so prized. And it’s also why the Volt’s 2016 improvement is so welcome. “I said that if they could improve the overall EV range, it would make one of my favorite cars even better,” Miller-Christiansen said. “To my amazement, they’ve done it.”

A Chevy Volt photographed in Alaska, perhaps the worst state for EV range, at least in the winter. (Photo: John Blehler/flickr)

Jeremy Michalek of Carnegie Mellon University, co-author of the EST study, told me, “Climate is one extra factor that electric car buyers should consider depending on where they live. It’s a challenge for extending the electric car’s territory in some parts of the country, because buyers may experience certain days when the range is quite a bit less than rated. In California, where most of the sales are happening now, even on the worst days of the year the range is still mostly good.”